Rotary electric machines including electric motors, generators, and the like have employed permanent magnets for some time. These machines take on many different topologies, the two most common topologies that use internal rotors being “Surface Permanent Magnet—SPM” and “Interior Permanent Magnet—IPM.” Additionally there is a topology “Interior PM—flux squeeze” that is also shown in the prior art. These topologies can be seen in the following patents and applications incorporated herein by reference:
U.S. Pat. App. No.2007/0057589shows IPMU.S. Pat. No.7,362,025shows IPMU.S. Pat. No.6,703,746shows IPMU.S. Pat. App. No.2009/0134731shows SPMU.S. Pat. No.7,486,037shows SPMU.S. Pat. No.3,072,813shows Interior PM-flux squeezeU.S. Pat. No.7,148,598shows Interior PM-flux squeeze
Generally high efficiency motors and generators use rare earth magnets that contain Neodymium (Nd) and Dysprosium (Dy) which are both expensive and which may be limited in supply at times. The lowest cost magnets per energy density are generally ceramic-based magnets. These magnets have lower magnetic properties than their rare earth counterparts but are readily available and inexpensive.
It is the general object of the present invention to provide a high efficiency rotary electric machine employing lower strength permanent magnets.
A further object of the invention is to provide rotary electric machines of the aforesaid type with magnet sections arranged in axially extending series for substantial enhancement of machine performance.
A further object of the invention is to provide a robust attachment means from the magnet sections to the shaft that does not short out the magnetic circuit.